A secondary battery easily applicable to various groups of products and having high energy density characteristics is commonly used not only in a portable device but also in an electric vehicle (EV) or a hybrid electric vehicle (HEV) which is driven by an electrical energy source. The secondary battery may not only greatly reduce use of fossil fuel but also produce no by-product after using energy, and thus is regarded as a new environment-friendly energy source capable of increasing energy efficiency.
Currently broadly used secondary batteries include a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel hydrogen battery, a nickel zinc battery, etc. An operating voltage of a unit secondary battery cell, i.e., a unit battery cell, is about 2.5V to 4.2V. Accordingly, if an output voltage higher than the operating voltage is required, a battery pack may be configured by connecting a plurality of battery cells in series. Alternatively, a battery pack may be configured by connecting a plurality of battery cells in parallel, depending on a charge/discharge capacity required by the battery pack. Therefore, the number of battery cells included in the battery pack may be variously set depending on a required output voltage or charge/discharge capacity.
In general, to configure a battery pack by connecting a plurality of battery cells in series or in parallel, a plurality of battery modules each including a plurality of battery cells are configured first and then a battery pack is configured by adding other elements to the battery modules.
A conventional battery module includes at least one cell cartridge configured to mount at least one battery cell therein and capable of guiding stacking of battery cells and of preventing motion of the battery cells. In general, a plurality of cell cartridges are provided to be stacked on one another, and guide stacking of a plurality of battery cells. The conventional battery module, which restrains the battery cell by using the cell cartridge, generally restrains motion of the battery cell by applying pressure in a surface direction of the battery cell.
FIG. 1 is a top view of a conventional cell cartridge 2 combined with battery cells 1, and FIG. 2 is a cross-sectional view taken along line II-II′ of FIG. 1.
Referring to FIGS. 1 and 2, the cell cartridge 2 is injection molded to have a form to fix corners of battery cell bodies, and corners of two battery cells 1 are fitted into the cell cartridge 2 to mount and accommodate the battery cells 1 in the cell cartridge 2. As such, in a conventional battery module, when the corners of the battery cells 1 are fitted into the cell cartridge 2, impact or vibration caused in the mounting process may be transferred to the corners of the battery cells 1, and the battery cells 1 may be damaged, for example, electrode assemblies or electrode leads 3 in the battery cells 1 may be broken.
Specifically, FIG. 3 is a magnified view of portion III of FIG. 2. Referring to FIG. 3, in a portion “a”, although x-direction motion may be restrained due to contact between a shoulder of the battery cell 1 and the cell cartridge 2, the thickness of a separator in the battery cell 1 may be reduced or a short-circuit may be caused by breakage of an electrode end when the battery cell 1 is continuously pressed.
Furthermore, as shown in a portion “b”, since the electrode leads 3 of the two battery cells 1 are welded to each other but bodies of the battery cells 1 are movable in the x direction due to vibration or impact, the electrode leads 3 of the battery cells 1 may be damaged.
In addition, as shown in a portion “c”, corners of the battery cells 1 contact an opposite object such as the cell cartridge 2. As such, if the battery cells 1 are swollen during charge/discharge of and between beginning-of-life (BOL) and end-of-life (EOL) stages of the battery cells 1, internal gas pocket regions may not be easily ensured and a short-circuit may be caused by damage of an ultrasonic-welded part in the battery cells 1. If the structure of the cell cartridge 2 is changed in such a manner that the corners of the battery cells 1 do not contact an opposite object such as the cell cartridge 2, the battery cells 1 may not be easily fixed in a length direction thereof.
Therefore, a method of preventing damage of a battery cell when the battery cell is mounted and accommodated in a cell cartridge is required.